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Etude des phénomènes couplés magnétothermiques dans les Supraconducteurs à Haute Température

Abstract : Theoretical study of HTS devices requires to solve magneto-thermal coupled equations. As coupling effects are very important in these materials, the development of numerical tools is almost unavoidable. A computer code based on the Finite Difference Method was developed in this direction, making it possible to solve 1D and 2D problems. It is then possible to numerically simulate the behavior of HTS.
Study of the losses in a Bi-2223 current lead, fed by an alternating current at 50 Hz, subjected to a DC magnetic field and immerged in a liquid nitrogen bath, is then carried out in a theoretical and experimental way. Thermal instabilities were observed experimentally. This phenomenon was studied starting from the search for the stable and unstable steady state solutions. For a given current and magnetic field, a maximum temperature above which recovery of the superconducting state is not possible could be defined.
YBCO pellets can trap strong magnetic fields and be used as very powerful cryomagnets. The dynamic response of these pellets, subjected to variations of a magnetic field, is studied in a detailed way (current density, magnetic field and temperature distributions). Results of the simulations show significant differences when the influences of the magnetic field and temperature are taken into account in the electrical law E(J). An optimum of the maximum magnetic field to apply leading to a maximum of trapped flux could be given. This information is of great interest as it enables the design of the most effective pulse magnetization device.
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Contributor : Kévin Berger <>
Submitted on : Thursday, December 18, 2008 - 2:55:30 PM
Last modification on : Wednesday, May 30, 2018 - 12:46:26 PM
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Kévin Berger. Etude des phénomènes couplés magnétothermiques dans les Supraconducteurs à Haute Température. Sciences de l'ingénieur [physics]. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10126⟩. ⟨tel-01754309v2⟩

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